1. Field of the Invention
The present invention relates to a radio resources allocating method, a radio resources allocating apparatus, and a mobile communication system and, more particularly, to a radio resources allocating method in which a base station capable of forming a plurality of directional beams by applying a directional antenna capable of adaptively varying directivity, to a reception-reception antenna, allocates radio resources to a plurality of mobile stations, a radio resources allocating apparatus for carrying out the method, and a mobile communication system comprising a base station with the radio resources allocating function.
2. Related Background Art
The conventional mobile communication systems used antennas to radiate omnidirectional beams, as transmission-reception antennas of base stations, and thus each base station performed scheduling of transmission and reception without the need for paying attention to detailed location information of a destination mobile station in a cell or in a sector as long as it was known that the destination mobile station existed in the cell or the sector.
On the other hand, when a directional antenna, e.g., an adaptive array antenna (Adaptive Array Antenna=AAA) is applied as a transmission-reception antenna of the base station, it becomes feasible to direct an antenna beam with sharp directivity to each mobile station existing in the cell or the sector. If interference power ratios between beams are small, i.e., if the beams are spatially separated from each other, with the directional beams being directed to the respective mobile stations, it becomes feasible to implement simultaneous transmission and reception of packet data to different mobile stations with the respective directional beams, without the application of code division multiplex or frequency division multiplex.
However, if a plurality of directional beams interfere with each other with the separate directional beams being directed to a plurality of mobile stations, there will arise the need for application of code division multiplex or frequency division multiplex or time division multiplex to the packet data. For this reason, in the field of the mobile communication systems adopting the directional antennas, there were demands for a technique of selecting destination mobile stations so as to prevent the directional beams directed to the respective mobile stations from interfering with each other, and allocating the radio resources to the mobile stations selected.
An object of the present invention is to provide a radio resources allocating method, a radio resources allocating apparatus, and a mobile communication system capable of selecting destination mobile stations so as to prevent directional beams directed to the respective mobile stations from interfering with each other in application of the directional antenna as described above, and allocating the radio resources to the mobile stations selected.